A PRELIMINARY programme is now available of the General Discussion on Colloidal Electrolytes to be held by the Faraday Society at University College, London, on September 27-29. Prof. H. Freundlich will deliver an introductory paper, and papers in the remaining sessions will be grouped according as they deal with theory, experimental technique or special subjects (soaps, dyestuffs, silicates, proteins, and so on). The papers, which will be available in advance, will be taken as read; each author will indicate a few points of special interest, after which the subject will be open for discussion. Among those outside Great Britain who are contributing papers are Dr. E. J. Bigwood (Brussels), Prof. P. Debye (Leipzig), Prof. E. Elod (Karlsruhe), Prof. A. Frumkin, Dr. Proskarnin and Prof. A. J. Rabinovith (Moscow), Prof. E. Hammarsten (Stockholm), Prof. H. R. Kruyt (Utrecht), Prof. Linderstrom-Lang (Copenhagen), Prof. A. Lottermoser (Dresden), Prof. J. W. McBain, Mrs. M. E. Laing McBain and Margaret M. Barker (Stanford University), Prof. W. Pauli (Vienna), Prof. M. Samec (Ljubljana), Prof. A. Treadwell (Zurich) and Dr. F. Valko (Ludwigshafen a/Rh.).